Things You Thought You Knew – Sonic BOOM!

Where does the wind come from? What is a sonic boom? Neil deGrasse Tyson and Chuck Nice explain things you thought you knew about sonic booms, daily temperatures, and how wind works.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Neil deGrasse Tyson?

  Hello Startalkians, Neil here. Coming up, we have another Things You Thought You Knew episode. This time, we're talking about sonic booms, day and night temperatures, and wind. Check it out.

• 0:16Neil deGrasse Tyson?

  Welcome to Startalk, your place in the universe where science and pop culture collide. Startalk begins right now.

• 0:29Neil deGrasse Tyson?

  I've come to shed some more light on that which is mysterious in this world.

• 0:35Chuck Nice?

  Yes, yes, the stuff you thought you knew, but you didn't know.

• 0:38Neil deGrasse Tyson?

  That's what you thought you did. So I just thought I'd talk about sonic booms.

• 0:41Chuck Nice?

  Okay.

• 0:42Neil deGrasse Tyson?

  What do you think of that?

• 0:43Chuck Nice?

  I love that.

• 0:44Neil deGrasse Tyson?

  Nobody doesn't love a sonic boom. Nobody does.

• 0:46Chuck Nice?

  Yeah, that is one of the best, most popular video games. That's Sonic.

• 0:49Neil deGrasse Tyson?

  That's Sonic.

• 0:50Chuck Nice?

  That's Sonic. I tell you, that hedgehog, he is something else.

• 0:54Neil deGrasse Tyson?

  So we can talk about sonic boom. So here you go. Ready? So let's take a airplane. That's a good, good choice here. And generally, airplanes make noise. And so you'll hear the noise and you'll look up and you see the plane coming.

• 1:09Chuck Nice?

  Right.

• 1:10Neil deGrasse Tyson?

  And then receding. All right. The fact that you heard the plane and looked up and then you see it approaching.

• 1:17Chuck Nice?

  Mm hmm.

• 1:18Neil deGrasse Tyson?

  Means the sound got to you ahead of the plane.

• 1:24Chuck Nice?

  Okay, yes.

• 1:25Neil deGrasse Tyson?

  Right? The plane is not where you are yet. It's down, it's down, it's down, down the road a bit, right? So you hear it. So the sound is going at the speed of sound. And in regular air, they call it 700 miles an hour. So it's around there.

• 1:41Chuck Nice?

  700.

• 1:42Neil deGrasse Tyson?

  700 miles an hour. And.

• 1:45Chuck Nice?

  The plane is still in like, what, four something?

• 1:47Neil deGrasse Tyson?

  Yeah, 500 miles an hour. So the sound is emanating in front of the plane relative to the plane at 200 miles an hour. Nice. Okay, all right, not a problem. No. This is very easy. We can, this is not hard to understand. All right, so let's ask the question, because by the way, there's 700 miles an hour is the speed of sound in air. Right. In typical sort of sea level type air. All right, that's the speed of sound. Now suppose the plane flew a little faster. Let's let it go 600 miles an hour. Okay. All right, well, the sound going in front of it is now moving in front at only 100 miles an hour faster.

• 2:30Neil deGrasse Tyson?

  Right, because it's, it's not going to increase because it's the speed of sound. Sound in air. In air. Okay, so what that means is the plane will be a little closer to you before you notice that it's there. Right. Okay, because it didn't get, it didn't have a chance to get too far ahead. All right, because the plane is like right, right coming up behind it, but it's still moving away from it at 100 miles an hour. That's still pretty fast. Okay. That's, that's fast. How about 650 miles an hour? So now, wait a minute. Now it's only, okay, how about 680 miles an hour? 690. Wait a minute. What happens if you go 700 miles an hour? What happens to the sound you're trying to emit in front of you?

• 3:14Neil deGrasse Tyson?

  Well, you can't emit, it's right with you. It's right with you. It is. Right. With you. So here's the sound you're trying to push forward and it's moving forward at 700 miles an hour, but so are you. So that plane approaches you. You don't even know it's there. You don't even know to turn around and notice it. Right. Until it is directly overhead. And then the sound from the, the, the, the sound hits you and the light from the plane hits you and there you are. You say, oh, there's a plane overhead. Right. Well, it's right there above you. All right, let's keep going. Let's, let's, let's not stop there. Now have it go 750 miles an hour. 800 miles an hour.

• 3:58Neil deGrasse Tyson?

  Oh, by the way, we have words for this. If you go the speed of sound, Mach 1. Nice. So now you have punched through this quote, "sound barrier." It's not really a barrier, but we used to think it was one. You punched through and now the sound lags behind. Right. Alright, so now the faster you go beyond Mach one, Mach two would be how fast?

• 4:22Chuck Nice?

  Twice the speed of sound.

• 4:23Neil deGrasse Tyson?

  Twice the speed of sound. So fourteen hundred, fifteen hundred. If you go twice as fast, then you are leaving the sound behind you.

• 4:32Chuck Nice?

  Right.

• 4:32Neil deGrasse Tyson?

  And all the sound that you are making is now snowplowed into this cone that comes out away from your vessel.

• 4:46Chuck Nice?

  So it's like your plane made a wake of nothing that is being filled with the sound that you left behind.

• 4:54Neil deGrasse Tyson?

  Correct. And on the edge of that is all the sound that would have spread out through space ahead of you. And now it's all compressed behind you.

• 5:07Chuck Nice?

  Oh.

• 5:08Neil deGrasse Tyson?

  And so now that plane flies overhead, you don't know it's there.

• 5:13Chuck Nice?

  Right. As a matter of fact, you won't know it's there because it didn't make a sound.

• 5:18Neil deGrasse Tyson?

  It didn't.

• 5:23Neil deGrasse Tyson?

  Brilliant Chuck. You're a fast study there. So there it is directly overhead. You don't even know to look up.

• 5:30Chuck Nice?

  Right.

• 5:30Neil deGrasse Tyson?

  And it goes, because it's well ahead of the sound it's making. So where's the sound it's making? Well, it's way behind. And it's all been snowplowed into this wall of sound, moving forward at the speed of sound. So the plane is now downstream from you. And you say, hmm, that's odd. That didn't make a sound. Bam. The sonic boom hits you.

• 5:57Chuck Nice?

  It's, oh, it's all the, it's like the, like the big ball of sound. It's a wall of sound.

• 6:05Neil deGrasse Tyson?

  It's a wall of sound. It's compressed because the plane left it behind. And all the sound that it would have made, that you would have heard ahead of it, is now all behind it, in a wall. And it all got plowed into itself. That, as it passes over you, is a sonic boom.

• 6:23Chuck Nice?

  Oh, man.

• 6:24Neil deGrasse Tyson?

  And the higher up the plane is, the more delayed that is the sonic boom. You'll come up here, sonic boom, look up, where's the plane? It was way down, way downstream.

• 6:36Neil deGrasse Tyson?

  Now, so turns out, anything that goes faster than sound will make a sonic boom. Okay. So it turns out a whip, the crack of a whip. Okay. Is the tip of the whip moving faster than the speed of sound. Oh, sweet. It's a mini sonic boom. We used to do in the locker room, you get like a rat tail with a towel. With a towel. So the sonic boom comes about, so the, the, the, the material, this would be true with the whip as well. As it flings forward and you, you start retracting it before it fully flings forward. And the rapid change of direction there is the thing moving just faster than the speed of sound.

• 7:17Neil deGrasse Tyson?

  And you hear a crack. It's very small. It's a sonic crack, not a sonic boom. So, so that's what a sonic boom is. And I love me some sonic booms, but we, you know, we had the, no, we didn't. We've never had a commercial, a commercial supersonic plane in the United States. But Europe did, and you know what that was? Uh, that French plane. The French plane. Yeah. The Concorde, S S T. The Concorde. And that was a collaboration, I think with England. And so it would fly to London and to Paris to New York. But we didn't have one of those planes. Right. We didn't have, so how are we going to compete with that? Here's what we do. We say, we don't like sonic booms over our residences.

• 7:59Neil deGrasse Tyson?

  So if you want to fly your plane over continental United States, you have to fly subsonic. Well, what the point, what's the point of that? Right. Okay. So you didn't have these planes going to LA. They all went to New York, basically. Right. And, and it would have been great if we can all fly supersonically. So the concern was you're having a nice peaceful afternoon, a picnic, and then sonic booms are just coming across. I think the novelty would probably wear off quickly.

• 8:26Neil deGrasse Tyson?

  Is my sense of this. Now, a quick little story before we end. There's the Salisbury Cathedral. This, I, I think this is a true story. I read about it long ago, but I haven't seen more written about it. So I don't know. Maybe it's apocryphal. The Salisbury Cathedral, one of the oldest cathedrals in the world, has one of the oldest cloths. In the world and I visited that when I visited Stonehenge when I was a kid. Because the Stonehenge is in the Salisbury Plains, uh, southwest England. So anyhow, the Royal Air Force, it's a very underpopulated area. So the Royal Air Force was doing maneuvers there and there were sonic booms that they were making all the time. Conservatives were worried, conservatives were worried that these sonic booms would jiggle the cathedral.

• 9:11Neil deGrasse Tyson?

  And, and damage it.

• 9:13Chuck Nice?

  Okay.

• 9:14Neil deGrasse Tyson?

  So we got some acoustic engineers that did some measurements. And sure enough, there's serious sonic boom energy coming into the cathedral. And then someone said, gee, I wonder how much vibration comes from lower C on their organ. On their pipe organ. So they tested the low notes on the pipe organ. And it was more energetic than the sonic booms coming across the thing. So that was the end of that conversation right there.

• 9:39Chuck Nice?

  Okay.

• 9:40Neil deGrasse Tyson?

  Now, it could be apocryphal, but it's a fun story. What it means is just in general. If you think something is causing something, look for anything else that could swamp that effect. And if you find something that does, then formulate another question.

• 9:54Chuck Nice?

  So now when a sonic boom of a meteor coming into our atmosphere.

• 10:00Neil deGrasse Tyson?

  That's why you'll never know. People say, oh, look, here it comes. No, you don't, you don't know until it's too late, until it already hits.

• 10:06Chuck Nice?

  So is it the boom that is breaking windows or is it the movement of air itself? Because it just.

• 10:12Neil deGrasse Tyson?

  It's the same thing. It's the same thing. It's a shockwave.

• 10:14Chuck Nice?

  It's still a shockwave.

• 10:15Neil deGrasse Tyson?

  It's a shockwave. That's correct. And you know something else? This is really cool. Okay, okay.

• 10:22Neil deGrasse Tyson?

  You know, the speed of light drops when it goes into transparent, solid materials. So speed of light is lower in glass. It's even lower in diamond.

• 10:30Chuck Nice?

  Right.

• 10:31Neil deGrasse Tyson?

  Okay. Now suppose you have a particle that you send through that material that goes faster than the speed of light.

• 10:39Neil deGrasse Tyson?

  Because you can do that. There's no rule against it. All right. It's not my fault. The light is slow.

• 10:45Neil deGrasse Tyson?

  That's not my fault. I'm obeying Einstein. I don't care that we're in glass or in diamond or in water. Okay, so it turns out when particles do that, they make a kind of sonic boom of their own, but it's not sonic. It's light.

• 11:00Chuck Nice?

  A light boom?

• 11:01Neil deGrasse Tyson?

  Yeah, it's a light boom.

• 11:02Chuck Nice?

  Oh.

• 11:02Neil deGrasse Tyson?

  It's a light boom.

• 11:03Chuck Nice?

  Well, that sounds delightful.

• 11:06Neil deGrasse Tyson?

  And so it's a similar phenomenon, but it's happening sort of electromagnetically. And it admits its own kind of radiation for having done so. So it's a more general phenomenon and a principle shockwaves. It's all part of the same discussion of going faster than the medium wants you to go. And there you have it.

• 11:27Chuck Nice?

  That's very cool. Well, you know, a light boom, you know, in production, there's a stand that you hang a light on.

• 11:36Neil deGrasse Tyson?

  I guess so. That's a real, a really boring version of the definition of the word.

• 11:41Chuck Nice?

  I was gonna say that like your light booms are way better than mine.

• 11:45Neil deGrasse Tyson?

  Way cooler than the sound guy's booms.

• 11:47Chuck Nice?

  Right.

• 12:03Speaker 02

  Hi, I'm Ernie Carducci from Columbus, Ohio. I'm here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon.

• 12:13Neil deGrasse Tyson?

  This is StarTalk with Neil deGrasse Tyson.

• 12:26Neil deGrasse Tyson?

  Chuck.

• 12:27Chuck Nice?

  Yes.

• 12:28Neil deGrasse Tyson?

  What time of day is the sun the highest in the sky?

• 12:33Chuck Nice?

  Oh, I don't know. High noon.

• 12:34Neil deGrasse Tyson?

  High noon. Yeah, high noon. And unless it's daylight savings time, and then it's like one o'clock.

• 12:40Chuck Nice?

  Okay.

• 12:41Neil deGrasse Tyson?

  What's the hottest time of day?

• 12:44Chuck Nice?

  Normally around three o'clock.

• 12:46Neil deGrasse Tyson?

  Why isn't it when the sun is at its highest?

• 12:50Chuck Nice?

  Why are you doing this to me?

• 12:52Neil deGrasse Tyson?

  I'm just trying to.

• 12:54Chuck Nice?

  What is this? Why are you grilling me? No, let me think here.

• 13:00Neil deGrasse Tyson?

  When the sun is at its highest point in the sky, it is maximally heating the earth.

• 13:05Chuck Nice?

  Oh, well, then that makes sense because if it's at that point that it starts to maximally heat the earth, then it would take a little longer for the earth to actually. No, that don't make no sense. I take it back. Uh, I'm trying to think here. Why would it be?

• 13:21Neil deGrasse Tyson?

  Because every moment after that, it's heating the earth less. That's all I'm saying. That's all I'm saying. Until sunset, when it's not heating the earth at all, not your side of the earth at least.

• 13:30Chuck Nice?

  Right.

• 13:31Neil deGrasse Tyson?

  So, okay, so I would explain.

• 13:33Chuck Nice?

  Well, so my explanation was correct.

• 13:34Neil deGrasse Tyson?

  Well, but not for why, not.

• 13:37Chuck Nice?

  Not for why?

• 13:37Neil deGrasse Tyson?

  Yes, but no.

• 13:39Chuck Nice?

  Yes, but no. I got you.

• 13:40Neil deGrasse Tyson?

  All right, here it goes.

• 13:41Chuck Nice?

  It was a valiant effort.

• 13:42Neil deGrasse Tyson?

  Okay. So, but. The sun emits a lot of bands of light, but primarily emits light in the visible part of the spectrum. And we all know that those are the colors of the rainbow.

• 13:53Chuck Nice?

  Yes, one of my favorite stories, and it's not a story. One of my favorite recountings that you have done, and I believe you did it on the first season of Cosmos, was the scientist who was measuring the light and then outside of the spectrum that he was recording, there was a temperature change. And he knew then because of that, that there had to be a light that we don't know or see that is making this change. I love that. I just love that recounting.

• 14:24Neil deGrasse Tyson?

  And he said it in his very sort of 18th century flair. He called it light unfit for vision.

• 14:30Chuck Nice?

  Light unfit for vision?

• 14:31Neil deGrasse Tyson?

  Is that cool? Yeah, so he discovered infrared light, and it was William Herschel.

• 14:35Chuck Nice?

  William Herschel, yes.

• 14:36Neil deGrasse Tyson?

  Yeah, all right. So, here's the thing. The, so the sun emits infrared, which we can't see, emits ultraviolet, which we can't see. And both of those are bands of light outside of the bands we do see. So it's red, orange, yellow, green, blue, violet. All right.

• 14:52Chuck Nice?

  Roy G. Biv.

• 14:53Neil deGrasse Tyson?

  And the, Roy G. Biv. And the sun peaks right there in the middle, between yellow and green. All right. So, so more energy comes from the sun right there in yellow and green than in any other part of the spectrum. All right. The fact that you can see the sun through the atmosphere means the air is not absorbing any of that energy.

• 15:20Neil deGrasse Tyson?

  Well, if the air is not because you can see the sun, it got through the atmosphere to the bottom, to the base of the atmosphere where your eyeballs are, to know what, so the light comes all the way through. It's not getting absorbed by the atmosphere. It hits the ground. And the ground absorbs the sunlight. Ah. Not the air. Ah. Okay, so now, the ground absorbs the, the, the, the yellow light and the green light and the blue light and the red light, absorbs it all. That heats the molecules on Earth's surface. Then the molecules re-radiate that same energy, but in a different part of the spectrum. Interesting.

• 16:03Neil deGrasse Tyson?

  It re-radiates it as infrared. Wow. And the infrared gets absorbed by the atmosphere. So there's a time delay. Right. Between when the sun is slamming us with a visible light and when Earth's surface responds back with infrared, heating the air. Now you put the thermometer in the air, you say, oh, the temperature is going up. Did it go up at tw- at high noon? No. No. Took a couple of hours. Wow. For that to build. That, so, I, I had, see, kids, this is why you gotta go to school. Yeah, okay. This is why you gotta go to school so that you can actually learn things the

• 16:48Neil deGrasse Tyson?

  proper way to learn them. I'm not done yet. Get out. Okay, so, if that's the case, that means the farther away you are from Earth's surface. Right. The cooler it's gonna be. The cooler it's gonna be. Right. You ever go from sea level to a mountaintop? Oh, God, yes, it's lovely. Okay, the temperature dropped. What a refreshing climb. Okay. You say, no, I've never hiked it, I've, I've taken a tram, but I'm not hiking it. Oh, hell no. So generally, it's cooler on mountaintops because it's farther away from the general Earth's surface that's there. Not only that, if you go up in an airplane. Well, forget it. If you ever looked at the temperature gauge that sometimes they show in the front of the, you know, at the bulkhead, uh, you'll see the temperature drop, it'd be forty below zero.

• 17:33Neil deGrasse Tyson?

  Yeah, exactly. Just a few miles up. Why is it so cold up there? Is it because you're closer to space? No. No, it's because you're farther away from where the sunlight is actually due in the heating, and that's right above the earth's surface. In fact, in meteorology, there's a rule about how high above earth's surface you have to put the thermometer so that everybody can get a consistent reading.

• 17:56Chuck Nice?

  Interesting.

• 17:57Neil deGrasse Tyson?

  It's not, it's not directly above the ground. You gotta pull it up a little so there's some mixing of the air so that everybody can get a nice, consistent, sensible reading of the temperature.

• 18:07Chuck Nice?

  I love that.

• 18:08Neil deGrasse Tyson?

  I'm not done yet.

• 18:09Chuck Nice?

  Oh, get out!

• 18:10Neil deGrasse Tyson?

  Okay, so now watch. Infrared. Do you know what traps infrared? Greenhouse gases.

• 18:17Chuck Nice?

  Uh oh.

• 18:18Neil deGrasse Tyson?

  Do you know what the predominant number one greenhouse molecule in the atmosphere is?

• 18:24Chuck Nice?

  Uh, water vapor.

• 18:25Neil deGrasse Tyson?

  Water vapor?

• 18:26Chuck Nice?

  Yeah.

• 18:27Neil deGrasse Tyson?

  The water molecule. Okay, so let's do an experiment. Let's take away the water molecules from where you are. There's a word for such places. What are they called?

• 18:39Chuck Nice?

  Deserts.

• 18:39Neil deGrasse Tyson?

  Deserts. Thank you. So, the temperature rises in mid-afternoon in the desert, then the sun sets. What happens to that heat that the ground had accumulated from the sun? It gets reradiated as infrared. Does it get trapped? No.

• 18:57Chuck Nice?

  No.

• 18:58Neil deGrasse Tyson?

  It escapes, and the nighttime temperature in the desert plummets.

• 19:03Chuck Nice?

  Yes. And that is the weirdest thing about the desert, is you will die of a sunstroke during the day, and you will die of overexposure at night.

• 19:14Neil deGrasse Tyson?

  Hypothermia at night.

• 19:16Chuck Nice?

  Hypothermia at night.

• 19:17Neil deGrasse Tyson?

  You gotta be ready for a 40-degree range of temperature from maximum heating in the afternoon, of maximum warming of the air, to when everything just radiates away. And by the way, when there's no sun, you're just losing heat. So therefore, the coldest time of the day is when?

• 19:37Chuck Nice?

  Um, I'm going to say in the, well, the coldest time of the day.

• 19:40Neil deGrasse Tyson?

  Of the 24 hour day. When is it?

• 19:42Chuck Nice?

  Um, 12 midnight or 3 o'clock in the morning, 3 o'clock in the morning.

• 19:47Neil deGrasse Tyson?

  No, no, just before sunrise.

• 19:49Chuck Nice?

  Oh, yeah, because there's been no sun all that time.

• 19:51Neil deGrasse Tyson?

  No sun. It's been cooling off the whole time.

• 19:53Chuck Nice?

  The entire time.

• 19:54Neil deGrasse Tyson?

  Take a look at temperature plots.

• 19:56Chuck Nice?

  Right, exactly.

• 19:56Neil deGrasse Tyson?

  Okay, it'll peak in the mid afternoon and it'll, no matter where you are, it'll do that. And then it'll go to its lowest point just before sunrise. And then the sun starts giving you the energy again.

• 20:07Chuck Nice?

  See, that's, I, I gotta stop overthinking things because I'm talking to you and I'll, I'll start overthinking.

• 20:12Neil deGrasse Tyson?

  I get basic questions. I'm not trying to, these aren't trick questions.

• 20:15Chuck Nice?

  I know.

• 20:16Neil deGrasse Tyson?

  Okay.

• 20:17Chuck Nice?

  But it's still, yeah, but you're right. Yeah, that the sun has not been present all that time. It makes sense that just before the reappearance of the sun, that will be the coldest time.

• 20:26Neil deGrasse Tyson?

  Correct. And I gotta correct something that people have gotten wrong.

• 20:29Chuck Nice?

  Okay.

• 20:30Neil deGrasse Tyson?

  They'll say, when is the darkest time of night?

• 20:34Chuck Nice?

  Just before the dawn.

• 20:36Neil deGrasse Tyson?

  No, see, that's bullshit. Okay.

• 20:40Neil deGrasse Tyson?

  That's bullshit. Okay, sorry. All right. Anytime it is not twilight, you are basically equally as dark the entire night.

• 20:49Chuck Nice?

  No matter what.

• 20:50Neil deGrasse Tyson?

  So you, so you want, pick midnight if you want, fine.

• 20:54Chuck Nice?

  Right.

• 20:54Neil deGrasse Tyson?

  But that whole time you are good to go. None of this, the darkest is just before dawn.

• 20:58Chuck Nice?

  Just before the dawn.

• 20:59Neil deGrasse Tyson?

  Yeah, it's just bullshit. Right, right.

• 21:00Chuck Nice?

  Yeah, exactly.

• 21:01Neil deGrasse Tyson?

  That's what I'm saying. It's the darkest in the room just before I turn on the light. Well, it was dark that whole time before you turned on the light.

• 21:07Chuck Nice?

  Right, exactly. Yeah, that.

• 21:10Neil deGrasse Tyson?

  All right. So, but wait, I'm not done. There, there are certain places like Hawaii and Iceland where the range from the high to the low temperature in any 24 hour period is very narrow. Check out the, the, the climate data for those two places.

• 21:29Chuck Nice?

  I, I know this for a fact, but go ahead.

• 21:31Neil deGrasse Tyson?

  And so, so why?

• 21:33Chuck Nice?

  Oh, I don't know. I I just used to stay in Hawaii for a bit. I spent a few months living there.

• 21:38Neil deGrasse Tyson?

  Uh huh. Yeah, be like seventy six in the daytime and maybe sixty eight at night.

• 21:43Chuck Nice?

  Yeah.

• 21:44Neil deGrasse Tyson?

  You know, and so that's because they're in the middle of the oceans and the ocean has very high humidity that stabilizes the the the flow of the heating between day and night.

• 21:56Chuck Nice?

  Oh, I got you.

• 21:57Neil deGrasse Tyson?

  It slows it down. So so you heat your so the the I've done this even as a New York City resident. Okay, the way you want to minimize the temperature drop is you have a perfectly a sunny day. Then at sunset, moist clouds come in. Then they'll trap the heat you.

• 22:17Chuck Nice?

  Hold the heat.

• 22:18Neil deGrasse Tyson?

  Then they'll hold the heat overnight.

• 22:20Chuck Nice?

  That's hot. I mean, that's cool.

• 22:22Neil deGrasse Tyson?

  I mean.

• 22:24Chuck Nice?

  That's great.

• 22:29Neil deGrasse Tyson?

  So this is why you get huge temperature swings it in in the deserts, why you don't in humid climates, the tropics, and of course, in island nations. It's also why it's hotter a couple hours after the middle of the day than right at the middle of the day. And one other thing. The day of the year where the arc of the sun is longest and highest in the sky is the first day of summer, June twenty first.

• 22:55Chuck Nice?

  That's right.

• 22:56Neil deGrasse Tyson?

  Uh Chuck, what is the hottest month of the year, at least in the northern hemisphere?

• 23:01Chuck Nice?

  Uh August.

• 23:02Neil deGrasse Tyson?

  Yeah, it's not June.

• 23:03Chuck Nice?

  It's not.

• 23:03Neil deGrasse Tyson?

  It's not even really July. It's August.

• 23:05Chuck Nice?

  It's August.

• 23:06Neil deGrasse Tyson?

  For the same reason climatically, what goes on in a daytime cycle actually goes on in a seasonal cycle.

• 23:14Chuck Nice?

  So well.

• 23:15Neil deGrasse Tyson?

  You have maximum ground heating in June, but there's a lag between the ground heating and the ground responding to this and and and seasonally that takes a couple of months to build.

• 23:29Chuck Nice?

  Not to mention the ocean temperatures in those areas.

• 23:31Neil deGrasse Tyson?

  Also delayed.

• 23:32Chuck Nice?

  Right.

• 23:33Neil deGrasse Tyson?

  Also delayed.

• 23:34Chuck Nice?

  Super cool, man.

• 23:35Neil deGrasse Tyson?

  Do you have it?

• 23:36Chuck Nice?

  I I thought this was gonna be a boring one.

• 23:42Neil deGrasse Tyson?

  I did. This is great. I don't want to let you down here. And I didn't title this one. This is like the temperature during the day.

• 23:51Neil deGrasse Tyson?

  Okay, we need a better, oh, we need a better title than the temperature during the day. Right, right. And so, and why it's cold. How about fun with Fahrenheit? Oh, I like that. Fun with, fun with Fahrenheit. With Fahrenheit. And so, and like I said, when you're in an airplane, you're so far away from the ground. The ground had no chance of heating the air you're flying in. Right. And so it could be 40 below. Yeah. Up at, you know, five miles up where you're flying at 30,000 feet. And one final thought. Go ahead. Okay, do you know the temperature, the Fahrenheit and Celsius temperature scales? Correct. You know, they're different, right? But do you know they actually cross on a graph? I did not know that. Okay. Because I thought they were running parallel.

• 24:36Neil deGrasse Tyson?

  Yeah, they're not parallel. No, it's Celsius is parallel to Kelvin, but Celsius is not parallel. Parallel to Fahrenheit. To Fahrenheit. So, so, so for example, what is it? Boiling water is what Fahrenheit? Two 12. And it's 100 Celsius. And what's the temperature diff, what's the degree difference between those? 112 degrees. 112 degrees. On Celsius, what temperature does water freeze? Zero. What, on Fahrenheit, what temperature does it freeze? Oh, 32. So what's the temperature difference there? That's only 32 degrees. So, so the difference between Celsius and Fahrenheit is shrinking as you get colder. Closer. Ah. Okay, there is a temperature where if you plotted this, those two graphs cross. Cross? That makes sense.

• 25:19Neil deGrasse Tyson?

  Which means at that temperature, they're equal each other numerically. And that temperature is exactly 40 below. Nice. So when I say, oh, it's 40 below, and you say, oh, what's a Fahrenheit or temperature? I might just mess with your head. Make a difference. Doesn't matter. Doesn't matter. So cold, doesn't matter. This gotta matter. And then I say, do the math. And there's a little formula to convert Fahrenheit to Celsius. And if you put in one temperature, you get the other. If you put in 40 for one of them, but minus 40. Minus forty comes out the other side. So it's an equation at that point that gives you the same answer going in as coming out. It's very cool.

• 25:54Chuck Nice?

  Yo, man, I'm getting a T-shirt that says, I'm forty below because I'm cool anywhere, baby.

• 26:00Neil deGrasse Tyson?

  I'm cool Celsius or Fahrenheit.

• 26:03Chuck Nice?

  I'm ice cold anywhere. All right.

• 26:28Neil deGrasse Tyson?

  Ask me where wind comes from.

• 26:30Chuck Nice?

  Oh, I know. It's it's my uncle and

• 26:37Chuck Nice?

  dude thinks it's funny. He's kind of rude. Doesn't make a difference if we're at the table or not. It's terrible.

• 26:44Neil deGrasse Tyson?

  Doesn't apologize or nothing.

• 26:45Chuck Nice?

  Doesn't apologize or nothing. Sometimes he's proud of it. Not cool. Not cool. Not cool.

• 26:56Neil deGrasse Tyson?

  Okay, ask me about meteorological wind.

• 26:58Chuck Nice?

  Okay, where where does meteorological wind come from?

• 27:04Neil deGrasse Tyson?

  I will quote Ogden Nash.

• 27:07Chuck Nice?

  Ogden Nash?

• 27:09Neil deGrasse Tyson?

  Yes, yes, the playful poet. Ogden Nash, wind is caused by trees waving their branches.

• 27:20Chuck Nice?

  That guy was stupid.

• 27:29Chuck Nice?

  Let me tell you right now, I do not know where wind comes from. I'm be honest. I don't know where wind comes from, but I know this much. It don't come from trees waving. Hey, how y'all doing?

• 27:43Neil deGrasse Tyson?

  How would you know?

• 27:44Chuck Nice?

  Because, and I'll tell you why.

• 27:46Neil deGrasse Tyson?

  This is important. This is a bit of science here.

• 27:48Chuck Nice?

  Okay.

• 27:49Neil deGrasse Tyson?

  You, how do you, when it's windy out? Trees are swaying.

• 27:54Chuck Nice?

  Right.

• 27:55Neil deGrasse Tyson?

  So how do you, how would you test what the cause and effect is of that?

• 27:59Chuck Nice?

  Because two things. One.

• 28:02Neil deGrasse Tyson?

  Wind could be caused by fast spinning anemometers. Okay, the, the, the we- weather veins. It could be, you know.

• 28:10Chuck Nice?

  Uh, it could also be caused by a butterfly flapping its wings in Ja- in, in Japan.

• 28:16Neil deGrasse Tyson?

  A big butterfly.

• 28:18Chuck Nice?

  Mothra.

• 28:19Neil deGrasse Tyson?

  Mothra.

• 28:22Chuck Nice?

  The moth's up across Tokyo. Um, no, the, the, the reason is because I hear the wind and then I see the tree move. So that means the wind was there.

• 28:34Neil deGrasse Tyson?

  The wind ain't about what sequence you obtained data.

• 28:39Neil deGrasse Tyson?

  The wind didn't hit your ear first and the tree's waiting for it to get through your head and then hit it.

• 28:44Chuck Nice?

  Sometimes it does. Sometimes I hear the wind and then I see the tree move. I'm like, that something came by me. Something came by me and moved that tree.

• 28:54Neil deGrasse Tyson?

  Those are the trees a quarter mile away.

• 28:57Chuck Nice?

  Could be.

• 28:59Neil deGrasse Tyson?

  All right, so no, this is very, uh, i- it's actually very simple.

• 29:03Chuck Nice?

  Okay.

• 29:03Neil deGrasse Tyson?

  Uh, you have wind, which is a, a re-adjustment of air pressure. It's really what's going on.

• 29:13Chuck Nice?

  Okay, so I don't, see, you say it like that mean, you say it like that just explained it to me.

• 29:21Neil deGrasse Tyson?

  Sorry, okay.

• 29:22Chuck Nice?

  You're like, no, no, what you have is, uh, basically a readjustment of air pressure. That's, that's all. That's what it is.

• 29:29Neil deGrasse Tyson?

  That's all it is, we're done here.

• 29:30Chuck Nice?

  Done.

• 29:31Neil deGrasse Tyson?

  No.

• 29:31Chuck Nice?

  Thanks.

• 29:32Neil deGrasse Tyson?

  So it's the unequal heating of Earth's surface.

• 29:35Chuck Nice?

  Oh, now that makes sense.

• 29:37Neil deGrasse Tyson?

  That's, that's what it is, okay?

• 29:40Chuck Nice?

  That's cool.

• 29:40Neil deGrasse Tyson?

  And so if it's warmer in one place than another,

• 29:46Neil deGrasse Tyson?

  and plus Earth is rotating, so these factors conspire so that if air ever rises.

• 29:58Neil deGrasse Tyson?

  Well, that wouldn't cause wind as we know it because wind goes horizontally to the surface. But if you have rising air, because it just got heated, what happened, what has to happen next? You don't, you don't create a vacuum blow. Well, you do, but then what happens?

• 30:14Chuck Nice?

  You have falling air.

• 30:16Neil deGrasse Tyson?

  Well, sorry, yes.

• 30:19Neil deGrasse Tyson?

  If air rises, you'll also have falling air. That's true. In total, but the pocket of, the, the pocket of atmosphere directly below where the air had gone up. Okay. What happens there?

• 30:33Chuck Nice?

  Oh, it has to be filled.

• 30:35Neil deGrasse Tyson?

  It's gotta be filled.

• 30:35Chuck Nice?

  So you get an updraft.

• 30:36Neil deGrasse Tyson?

  Gets filled from the sides.

• 30:38Chuck Nice?

  Right. Oh.

• 30:39Neil deGrasse Tyson?

  From the sides.

• 30:40Chuck Nice?

  Sweet.

• 30:42Neil deGrasse Tyson?

  Yes.

• 30:43Chuck Nice?

  Oh, my God. That's how it works? Yes. That's so cool.

• 30:49Neil deGrasse Tyson?

  Yes.

• 30:52Chuck Nice?

  I'm telling you, Earth is tricky. Earth is tricky. Earth got some tricks.

• 30:57Neil deGrasse Tyson?

  So you have rising air. It creates a partial vacuum, other, which is a pressure difference. And then other air says, we have to fill that gap. Let's go there. And so there it goes. Okay.

• 31:10Chuck Nice?

  Nice.

• 31:11Neil deGrasse Tyson?

  So if you look at hurricanes, for example, very, very low pressure in the middle. You have heated, warm, but the warm, moist, what we call unstable air. Air is unstable. It rises. Okay. In that low pressure system, all the clouds in the neighborhood want to go there.

• 31:35Chuck Nice?

  Sweet.

• 31:36Neil deGrasse Tyson?

  Ev- everything wants to go to the San Urban Hurricane.

• 31:39Chuck Nice?

  It's the cloud nightclub.

• 31:43Chuck Nice?

  Yo, man, you going to the eye tonight? You going to the eye? Yo, yo, man, I heard the eye is gonna be hot tonight.

• 31:54Neil deGrasse Tyson?

  So all the clouds try to come in, but then Earth's rotation sort of veers them to the right. No matter which way they're trying to head into the front entrance of the I Club. They veer to the right and so you have this circulation while the clouds are trying to get to the middle. And this gives you that spiraling storm, that spiral effect and everybody trying to get into the middle. And so hurricanes have famously fast winds because of this. Like hundreds of miles an hour in the fastest of them, fastest of them.

• 32:33Neil deGrasse Tyson?

  Now, if you have, if you have air that is descending, okay? Air that descends, first it won't make a cloud, okay? So descending air is like generally clear skies. Deserts have descending air, okay? Now, there's certain parts of the world where the descending air is so sort of total. It is sort of gently descending and it can go out the sides. But if the area of the descending air is large enough, then there's no sideways wind.

• 33:13Chuck Nice?

  Wow.

• 33:14Neil deGrasse Tyson?

  These areas of Earth's surface, especially over the ocean, are called the doldrums.

• 33:21Chuck Nice?

  That's the club that nobody wants to go to.

• 33:24Neil deGrasse Tyson?

  Sorry, you got the Hurricane I and you got the doldrums.

• 33:28Chuck Nice?

  It's like, man, I couldn't get into the I last night and now I gotta go to the doldrums.

• 33:33Neil deGrasse Tyson?

  The doldrums, so the doldrums are regions of Earth's surface where all the wind has ceased. And if you happen to be a sailing ship that wanders into the doldrums.

• 33:45Chuck Nice?

  Wow.

• 33:46Neil deGrasse Tyson?

  Oh my gosh.

• 33:47Chuck Nice?

  That's bad stuff.

• 33:48Neil deGrasse Tyson?

  That's it, that's it. Many a ship have just given up the ghost in the doldrums. Because you can't, you can't move and if they don't have oars, there's no wind, nothing, nothing. And they eat up their food supply, they eat each other, whatever, and that's it.

• 34:07Chuck Nice?

  Wow, it's like the great, it's like the great wind garbage patch of the ocean.

• 34:14Neil deGrasse Tyson?

  Like the plastic patch.

• 34:15Chuck Nice?

  Plastic patch, it just accumulates and goes nowhere.

• 34:24Chuck Nice?

  It's the wind.

• 34:25Neil deGrasse Tyson?

  I've thought of it that way.

• 34:27Chuck Nice?

  Yeah, that's terrible.

• 34:27Neil deGrasse Tyson?

  It's a fascinating, fascinating disturbed analogy.

• 34:30Chuck Nice?

  It is, yes. Oh, that's terrible, though.

• 34:34Neil deGrasse Tyson?

  Now, a couple of things, a couple of other things. So Mars has famously large windstorms. And we call them dust storms because the wind picks up the dust. You know, the Martian surface dust. Yeah, yeah, and so you can see this. In fact, when it happens, it cloaks the Martian surface. And so our telescopes and space probes, we can't see what's at the bottom. It's basically one of these like sandstorms you've read about in the desert. But it's like a dust storm on Mars.

• 35:06Chuck Nice?

  Or it's a very clever cloaking device that the Martians use to stop us from looking at them when they're doing stuff on the surface of Mars.

• 35:15Neil deGrasse Tyson?

  Yeah, exactly, Chuck. That's.

• 35:20Neil deGrasse Tyson?

  But do you remember the face on Mars? Listen, do you remember the face on Mars? So it was back in the seventies. There was like the famous face on Mars. It was like some kind of a, like a structure that had eye sockets and nose and a mouth. And it looked like a huge, it was huge, huge. And we got a couple of photos of it during the Viking missions. And everyone said, we gotta go back. Clearly, there's life there. Okay, by the way, if there's life and that represented it, it would have to be life that had sort of a simian face. Like, most life on Earth doesn't have a face. So that would be weird if life on a whole other planet had a humanoid face. That would just be weird, okay? Just saying.

• 36:04Neil deGrasse Tyson?

  But lobsters don't have, what, did we notice the lobster monument that was there? No, because we're only looking for stuff that looks like us. All right, so we went back. And you saw, and we had better, higher resolution, and you saw a hint of like where the eyebrows were in the mouth, but it was mostly sort of, and people said the Martians knew we were looking at them. Covered it up.

• 36:26Chuck Nice?

  They covered it up.

• 36:27Neil deGrasse Tyson?

  With their Mars dust. Here's my point. Uh, the Martian atmosphere is one one hundredth. The thickness of Earth's atmosphere.

• 36:36Chuck Nice?

  Oh, that's terrible. There's that's barely.

• 36:39Neil deGrasse Tyson?

  It is. So it's barely any atmosphere. So if you move that air a hundred miles an hour. Yeah, you ain't got.

• 36:46Chuck Nice?

  Yeah, it's like a, it's like a, it's like a infant trying to blow out a birthday candle, you know, just.

• 36:56Neil deGrasse Tyson?

  It's like.

• 37:01Chuck Nice?

  I'm giving up.

• 37:01Neil deGrasse Tyson?

  And that's why the whole scene in the movie The Martian where they can't leave, they're trying to leave the planet.

• 37:08Chuck Nice?

  Oh, don't do it.

• 37:10Neil deGrasse Tyson?

  A dust storm is coming. And then the rocket is rocking.

• 37:15Chuck Nice?

  Come on.

• 37:15Neil deGrasse Tyson?

  It's rocking back. And they take off and they get, and they gotta leave Mart Wadney on the surface because they're afraid they'll topple over from the wind.

• 37:24Chuck Nice?

  Oh, man, another movie ruined. Thank you, Neil.

• 37:27Neil deGrasse Tyson?

  No.

• 37:28Chuck Nice?

  Yeah, that can't happen then, right? That just can't even happen.

• 37:31Neil deGrasse Tyson?

  Yeah, yeah, it's not. Yeah, it's not happening. It might be dusty and you can't, you can't see.

• 37:36Chuck Nice?

  Yeah.

• 37:36Neil deGrasse Tyson?

  But you're not blowing over any spaceships.

• 37:38Chuck Nice?

  So it's also not gonna, it's also not gonna pick up a rod, a metal rod. And spear you with it because it's not gonna do that either.

• 37:50Neil deGrasse Tyson?

  Yeah, it's, it's not tornadoes. Right. So point is Mars is also an unevenly heated planet.

• 37:56Chuck Nice?

  And that's why you get.

• 37:57Neil deGrasse Tyson?

  And so, correct, correct.

• 37:59Chuck Nice?

  All right, wait a minute. Wait, wait, wait, wait.

• 38:01Neil deGrasse Tyson?

  What?

• 38:02Chuck Nice?

  I gotta ask you this now. All right. And this is off the explainer chart, but I gotta do it. Okay? I know that you know him. So did you ask him about that when he wrote this?

• 38:16Neil deGrasse Tyson?

  Like you're talking about, um, Andy Weir.

• 38:18Chuck Nice?

  Andy, yeah. Did, did you actually ask him?

• 38:24Neil deGrasse Tyson?

  I got all up in his situation, but then I, what I said was, what I said was, okay, Andy, so much else in that novel, later the movie, was, was so well calculated and thought through, I'm gonna give you a hall pass on this one.

• 38:41Chuck Nice?

  Oh, okay.

• 38:42Neil deGrasse Tyson?

  Because without it, he's got no story.

• 38:44Chuck Nice?

  Yeah, he's got, he had to do, it was, it was poetic license for a Mars hurricane, so he could get to the rest of the story.

• 38:51Neil deGrasse Tyson?

  Yeah, so I gave it to him because he did the rest of his homework. See, I'm not totally evil commentator. I will cut you some slack if you're an artist, as, as Mark Twain said, first get your facts straight, then distort them at your leisure.

• 39:09Chuck Nice?

  Okay.

• 39:10Neil deGrasse Tyson?

  That's Mark Twain's edict, so I'm all in on that. By the way, Venus is very evenly heated over its surface, and we think it has hardly any winds there at all.

• 39:20Chuck Nice?

  Nice.

• 39:21Neil deGrasse Tyson?

  Yeah.

• 39:22Chuck Nice?

  Yes, oh, yeah, it's, it's, it's a refreshing 900 degrees.

• 39:27Neil deGrasse Tyson?

  Well, you, you would vaporize, but ignoring that complication is...

• 39:33Chuck Nice?

  No wind needed, no wind needed. It's so even, it's so even.

• 39:37Neil deGrasse Tyson?

  It's so even.

• 39:39Chuck Nice?

  It's not a dry heat, it's an even heat, you're good.

• 39:41Neil deGrasse Tyson?

  That's the joke I heard about hell, they say, that, you know, you ask some evil person, how's hell? Yeah, yeah, it's, it's, it's, it's hot, but it's, it's low humidity, so we're fine.

• 39:55Chuck Nice?

  That's funny, actually.

• 39:56Neil deGrasse Tyson?

  Chuck, we gotta end it there, this is, this is a windy, starting off with your uncle.

• 40:06Chuck Nice?

  Yes.

• 40:07Neil deGrasse Tyson?

  We had a windy, a windy explainer for StarTalk. Dad, meet Chuck.

• 40:13Chuck Nice?

  Always a pleasure.

• 40:14Neil deGrasse Tyson?

  Neil deGrasse Tyson here. Keep looking up.